Virtual colonoscopy (VC) refers to a method of diagnosis based on computer simulation of standard, minimally invasive endoscopic procedures using patient specific three-dimensional (3D) anatomic data sets. Examples of current endoscopic procedures include bronchoscopy, sinusoscopy, upper gastro-intestinal endoscopy, colonoscopy, cystoscopy, cardioscopy, and urethroscopy. VC visualization of non-invasively obtained patient specific anatomic structures avoids risks, such as perforation, infection, hemorrhage, and so forth, associated with real endoscopy, and provides the endoscopist with important information prior to performing an actual endoscopic examination. Such information and understanding can minimize procedural difficulties, decrease patient morbidity, enhance training and foster a better understanding of therapeutic results.
In virtual endoscopy, 3D images are created from two-dimensional (2D) computerized tomography (CT) or magnetic resonance (MR) data, for example, by volume rendering. Present-day CT and MRI scanners typically produce a set of cross-sectional images which, in combination, produce a set of volume data. These 3D images are created to simulate images coming from an actual endoscope, such as a fiber optic endoscope.
It is desirable in virtual endoscopy, and especially in virtual colonoscopy, to determine a centerline as guide to the examination procedure. Prior techniques for calculating such a centerline typically utilize concepts of morphological operators, distance transform, minimum cost path, Dijkstra's algorithm, and so forth. References to such prior techniques can be found, for example, in Zhou et al., “Three-Dimensional Skeleton and Centerline Generation Based on an Approximate Minimum Distance Field,” The Visual Computer, 14:303-314 (1998); Truyen, T. Deschamps, L. D. Cohen. Clinical evaluation of an automatic path tracker for virtual colonoscopy. Medical Image Computing and Computer-Assisted Intervention (MICCAI), Utrecht, Netherlands, October 2001; Chen et al., “A Fast Algorithm to Generate Centerline for Virtual Colonscopy”, SPIE Conference, Feb. 12-18, 2000. Richard Robb, “Virtual (Computed) Endoscopy: Development and Evaluation Using the Visible Human Datasets”, Oct. 7-8, 1996. www.mayo.edu.; and in U.S. Pat. No. 6,514,082 entitled “System and method for performing a three-dimensional examination with collapse correction,” issued in the name of Kaufman et al., Feb. 4, 2003.